Commercial aircraft may generate and use a large amount of electrical power. For example, a large passenger or cargo airplane might generate over one megawatt of electrical power from its main engine sources. This power needs to be conditioned to be used by various users of power by Power Conversion Units (PCUs) and motor controllers.
The PCUs might convert an airplane's variable frequency high or medium voltage power to different frequencies and/or voltages. For example, a low voltage might be produced for powering equipment (e.g., lights, galley, cooling fans). High Voltage DC (HVDC) might also be produced to power large motor controller equipment to power hydraulic pumps, and various types of compressors. Low voltage DC (LVDC) might be produced to power avionics equipment and medium voltage DC (MVDC) might be powered to power electric brakes. One mechanism that might be used for power conversion is switching power converters that use Pulse Width Modulated (PWM) techniques.
Switching power converters that may be employed in the PCUs use a switching action that generates electromagnetic interference (EMI) noise that might interfere with normal operation of the aircraft (e.g., aircraft radio and navigational equipment). In order to help control this unwanted EMI noise, EMI filters are employed within the PCUs and motor drive systems. In some aerospace applications, such as on airplanes, EMI filters might account for 50% (or even more) of weight and volume in the power converters. EMI filter design for power conversion equipment for airplanes, or other aerospace applications, can be challenging due to stringent EMI requirements and volume and weight constraints that might be imposed on the power conversion and motor control equipment.